The impacts of extreme droughts can be dramatic. During August 2017 a team of researchers, including Ronaldo Sousa from CBMA, have been assessing the impacts of the 2017 drought on the critically endangered species Margaritifera margaritifera. Due to the extremely low flow conditions hundreds of organisms died near the banks of the Rivers Rabaçal and Tuela (NE of Portugal). The conservation implications of these mortalities will be further studied.